Project Summary/Abstract The heart is extensively innervated by the vagus nerve, and numerous vital heart-derived cues are actively sensed, including pressure fluctuations associated with every heartbeat, secreted peptides and signaling molecules, and pathological changes such as tissue damage, ischemia, and inflammation. Appropriate detection of heart signals is a first and key process in cardiovascular reflexes; however, the mechanisms by which the brain receives messages from the heart via the vagus nerve are still mysterious, and many essential questions about this heart-to-brain interface remain to be answered. Are different heart signals detected by different sensory neurons? What are the anatomical and molecular basis for sensing diverse cardiac inputs? How do distinct heart changes differentially regulate cardiovascular physiology? Here, we propose to bring knowledge and innovative technologies in neuroscience, physiology, genetics, and computational biology to this important interdisciplinary area to better understand the neural mechanisms that control cardiovascular functions. In preliminary studies, we identified two genetically distinct vagal sensory neurons subtypes marked by Npy2r and Piezo2 that both innervate the heart. Vagal Npy2r and Piezo2 neurons have fundamentally different gene expression patterns, electrical properties, and anatomical features and physiological roles in visceral organs other than the heart, suggesting they represent two distinct heart-to-brain pathways. Previously, we have developed a number of novel molecular and genetic techniques in the vagus nerve to enable cell-type specific studies for anatomy, neuronal activity, and physiological function of genetically defined vagal neuron populations. Here we will employ these powerful tools to determine, through three specific aims, whether vagal Npy2r and Piezo2 heart-to-brain neurons display distinct anatomical architectures, respond to different cardiac inputs, and differentially regulate a diversity of cardiovascular functions. We expect that studies proposed here will reveal many important details for two distinct vagal heart-to- brain circuits. We believe the proposed project will provide not only a critical foundation for delineating the underlying sensory mechanisms but also genetic access for charting distinct heart-to-brain neural circuits and precise modulation of cardiovascular functions. A molecular and functional dissection of the heart-to-brain axis will open up new vistas in this important area of neural control of the cardiovascular system and may bring novel concepts and therapeutic targets into the field of cardiovascular disease intervention and prevention.